Lect 6 Flashcards
Na+ regulation responds primarily to changes in what? What is the primary effector?
- blood volume/blood pressure
- primary effector: renin-angiotensin-aldosterone system
water regulation responds primarily to changes in what? What is the primary effector?
- osmolarity and volume of ECF
- primary effector: antidiuretic hormone
what is the function of aldosterone
- stimulates sodium reabsorption in the late distal tubule and collecting duct (principle cells)
- stimulates K+ secretion
- only 2% of filtered Na+ is under control of aldosterone
increases in what stimulate aldosterone release
- angiotensin II or plasma K+
what receptor does aldosterone bind to
intracellular mineralocorticoid receptor in principle cells
aldosterone-MR receptor complex stimulates transcription resulting in up-regulation of what four things
- apical ENaCs
- apical K+ channels
- NA+-K+-ATPase
- mitochondrial metabolism
aldosterone is antagonized by what diuretic
spironolactone
list the multiple effects of angiotensin II
- vasoconstrictor
- stimulates release of aldosterone
- stimulates Na+/H+ (NHE) exchange in proximal tubule
- stimulates thirst
- **functions favor salt retention and elevation of arterial blood pressure
angiotensin II levels are controlled by what enzyme
renin
renin is released by JGA via what 3 mechanisms: describe the intrarenal baroreceptors
- granular cells of JGA respond to pressure (stretch) in afferent arterioles
- release of renin inversely related to pressure in afferent arterioles
renin is released by JGA via what 3 mechanisms: describe the role of macula densa
- macula densa senses flow to distal tubule
- renin release inversely related to GFR
renin is released by JGA via what 3 mechanisms: describe the role of renal sympathetic nerves
- renal sympathetic nerves (RSN) end near granular eclls
- stimulation of RSN increases renin release via stimulation of Beta receptors
List out the RAAS pathway
angiotensinogen - (1) -> angiotensin I - (2) -> angiotensin II
- renin
- ACE
where is atrial natriuretic peptide released from? What is it released in response to?
- atria
- when pressures are high
what effect does atrial natriuretic peptide have on afferent and efferent arterioles
- ANP dilates the afferent arteriole and constricts the efferent arteriole
- increases GFR
how does atrial natriuretic peptide decrease NaCl reabsorption by the collecting duct
- directly inhibits secretion of renin and aldosterone
- directly inhibits Na+ uptake by medullary Collecting duct
what is the most important hormone regulating water balance
ADH
where is antidiuretic hormone released from? it is released in response to?
- pituitary
- when plasma osmolarity increases of plasma volume decreases
- *ADH has little effect on NaCl excretion
where are receptors for ADH located?
- basolateral membrane of collecting duct
- activation results in cAMP production
what two mechanisms sense changes in homeostasis and lead to release of ADH
- hypothalamic osmoreceptors sensitive to small changes in plasma osmolarity (1%)
- hypovolemia stimulates ADH secretion via arterial and left atrial baroreceptors
ADH has what functions
- increase permeability of the CD to water (aquaporins)
- increase Na+/Ka+2Cl- (NKCC2) transporters in the LOH
- increase permeability of inner medullary CD to urea
what is osmolar clearance and what is the equation?
- ml/min of blood plasma cleared of osmotically active particles
- Cosm = (Uosm)(V) / (Posm)
what does a reduced osmolar clearance indicate
- positive osmolar balance -> gaining osmoles -> progression to edema
- decreased GFR, increased aldosterone, or any disease that decreases the ability of the kidney to eliminate solue
what does a increased osmolar clearance indicate
- “dumping” osmolytes, leads to a loss of ECF
- diuretics, reduced aldosterone, or any disease that reduces the ability of the kidney to reabsorb normally
